Explosive arrangement for generating a mach stem to affect a line cut



A. A. LAVINE April 1, 1969 EXPLOSIVE ARRANGEMENT FOR GENERATING A MACH STEM TO AFFECT A LINE CUT Filed June 20, 1967 April 1, 1969 A. A. LAVINE 3,435,763

EXPLOSIVE ARRANGEMENT FOR GENERATING A MACH STEM Filed June 20, 1967 TO AFFECT A LINE CUT Sheet 3 of 3 INVENTOR. ARTHUR A, LA w/ve A 77'ORNEY April 1, 1969 A. A. LAVINE 3,

EXPLOSIVE ARRANGEMENT FOR GENERATING A MACH STEM TO AFFECT A LINE CUT Filed June 20, 1967 Sheet 3 of 5 6 INVENTOR.

A/e-mule A. AAV/NE A FOR/V5) United States Patent U.S. Cl. 102-24 Claims ABSTRACT OF THE DISCLOSURE There is described herein an explosive arrangement in which an elongated first high explosive charge member and an elongated second high explosive charge member are combined to provide a linear Mach stem extending along the length of the elongated second explosive charge member. The first explosive charge member has a detonation front velocity that is greater than the detonation front velocity in the second high explosive charge member. The Mach stem that is generated may be either a constant angle Mach stem or a variable angle Mach stem depending upon the particular type of wave shaping arrangement that is utilized and the Mach stem that is generated may be utilized to affect a line out in an article to be cut.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to the explosive art and more particularly to an explosive arrangement which may be provided in an elongated rigid or flexible configuration and in which an extended linear Mach stem is generated for cutting articles to be cut along a predetermined line.

Description of the prior art In certain applications it is often desired to perform operations upon materials by explosive means due to the comparatively high force and short reaction times usually associated with explosives. Among the applications in which explosive technology is utilized are explosive forming arrangements, explosive separation techniques and the like.

In the explosive separation techniques there is often a requirement that an article be separated or cut along a predetermined out line and the cutting should be done substantially instantaneously throughout the entire out line extending around the article. One field wherein such line cutting is often desired is in the removal of nose cones, heat shields, and the like from missiles or other vehicles during particular portions of their designed mission, that is, for example, it may be desirable to remove an ablative nose shield from a re-entry vehicle after the vehicle has passed through the thermally dangerous portion of the re-entry flight. Similarly, in missiles or antimissiles, it may be desired to remove nose cones or other protective devices surrounding the war head or guidance sections at predetermined times and generally, in such applications, it is necessary that the shield be completely removed within a very short and precisely known time period.

To accomplish this separation there have often been provided flexible line cutters in which an explosive was contained within a soft lead casing. The contained explosive could, due to the flexibility of the lead casing, be bent around into a ring-like annular shape to effect a line cutting along a predetermined peripheral cut line of, for example, a heat shield of a missile. The lead casing of the flexible line cutter was often provided in the configuration of a shaped charge arrangement and, therefore, it

Patented Apr. 1, 1969 was necessary that the flexible line cutter be spaced away from the article to be cut by appropriate stand-offs or the like. If the proper spacing from the article to be cut was not maintained by the stand-offs then the shaped charge would not have its effect and there would he no cutting of the article to be cut in such a section.

Further, if grease, oil or other contaminants happened to be present in the gap of the shaped charge then, of course, the shaped charge would not function as such and again proper cutting action would not be provided.

In applications wherein the explosive line cutter may be exposed to high intensity X-rays, it is equally apparent that lead would absorb the X-rays, heat and prematurely explode thereby rendering useless the entire mission upon which the line cutter Was utilized.

Therefore, there has long been a need for a line cutter arrangement, flexible in some applications and rigid in others, which could be comparatively easily fabricated and in certain applications, flexible enough to be bent into a ring-like annular configuration and which in any event, could be placed directly against the article to be cut in order to avoid problems associated with maintaining a suflicient stand-off position. Further, as can be seen from the above, it has also been long desired to provide an arrangement in which the presence of contaminants such as grease, oil or the like intermediate the explosive line cutter and the article to be cut would in general not alter the function of the line cutter or prevent its proper operation thereof. Such explosive line cutter should be comparatively insensitive to X-rays or similar such high intensity, short wave length electromagnetic radiation.

To the best of applicants knowledge, the above desiderata have not been heretofore available in flexible explosive line cutting arrangements.

SUMMARY OF THE INVENTION Accordingly, it is an object of applicants invention herein to provide an improved line cutting explosive arrangement.

It is another object of applicants invention herein to provide an explosive arrangement that may be conveniently positioned into a variety of configurations for cutting through an article along a preselected line.

It is another object of applicants invention herein to provide an improved explosive arrangement in which a Mach stem is generated to provide an eflicient line cutting operation.

The above and other objects of applicants invention are achieved, according to one embodiment of applicants invention, 'by providing a first explosive charge member that is generally rectangular in cross section and may be comprised of 90 to by weight of HMX explosive in a matrix of, for example, tetrafluoroethylene polymer. Such a configuration has been found by applicant to be sufficiently flexible to allow bending of the first explosive charge means into annular ring-like configurations, or other extended configurations as desired.

The first explosive charge means is generally provided in elongated, configurations to allow utilization thereof in extended line cutting operation.

In this embodiment of applicants invention the first explosive charge member is also provided with first preselected initiation surface areas on an external top surface thereof for initiation which, in this embodiment, may be a point initiation by a suitable initator to generate a detonation front upon the detonation thereof. The spherical detonation front initially travels through the first explosive charge member from the initiation surface area thereof both towards preselected interface surface area thereof spaced apart from said initiation surface area, and at right angles thereto along the longitudinal elongated length thereof. Thus there is provided a detonation front traveling along the elongated length between the external top surface area and the interface surface area.

In this embodiment of applicants invention the interface surface area is provided with a pair of side wall surface portions defining a slot extending a preselected distance into the first explosive charge member toward the top surface area and a base wall surface portion to define a base for the slot substantially parallel to the top surface area.

A second flexible high explosive charge member is positioned within the slot and has first preselected contact surface areas thereof in substantially continuous contact throughout the elongated length of the slot with the side wall surfaces and the base wall surface defining the slot in the interface surface area of the first explosive charge member. The second explosive charge member may be comprised, for example, of 90 to 80% by weight of PETN in a tetrafluoroethylene polymer binder.

The first explosive charge member defined above has a detonation front velocity on the order of 8500 meters per second and the second explosive charge member defined above has a detonation front velocity on the order of 6,500 meters per second, which is less than the detonation front velocity in the first explosive charge member.

In this embodiment of applicants invention, the configuration of the interface along the base wall surface portion and side wall surface portions of the first explosive charge member with the contact surface areas of the second explosive charge member provides the necessary wave shaping so that when the first explosive charge member is detonated and the detonation wave progresses to the interface a pair of converging, re-entrant detonation fronts are generated in the second explosive charge member moving from the contact surface areas toward a Mach stern emerging or second preselected external surface area. The Mach stem emerging preselected external surface areas may be aligned, in a line cutting application of applicants invention, on the article to be cut. along the predetermined cut line. As the detonation fronts in the second high explosive charge member move toward the second preselected external surface, they are swept back due to the difference in detonation front velocities in the first and second explosive charge members to converge along a line extending substantially throughout the elongated length of the flexible explosive arrangement and generate a Mach stern in this zone. As the line of convergence and the Mach stem move toward the second preselected external surfaces thereof, the momentum of the Mach stem continually increases due, in part, to the increasing density and pressure of the material within the Mach stern. As this material in the Mach stem contacts the article to be cut, the high momentum associated therewith effectively provides a linear cutting action along the out line. In this embodiment of applicants invention, it will be appreciated, the Mach stern so generated is a constant angle Mach stem.

In other embodiments of applicants invention, variable angle Mach stems may be utilized to provide the cutting action.

In still other embodiments of applicants invention there may be provided an inert member which, in conjunction with the first explosive charge member and second explosive charge member provides wave shaping for the detonation front in the second explosive charge member. Further, the explosive arrangement may be either flexible or rigid in a predetermined shape.

BRIEF DESCRIPTION OF THE DRAWING FIGURES 1, 1A, and 2 illustrate a flexible explosive arrangement according to one embodiment of applicants invention;

FIGURES 3 and 3A are perspective views, FIGURE 3 parially in section, of another embodiment of applicants invention;

FIGURES 3B and 3C illustrate another embodiment of applicants invention;

FIGURE 4 is a sectional view of the embodiment of applicants invention shown in FIGURES 3 and 3A; and

FIGURES 5 and 6 illustrate other embodiments of applicants invention.

Referring now to the drawing, there is shown, in the several figures thereof, several embodiments of applicants invention herein. For convenience in description applicant has selected the application of applicants invention as utilized in an annular or ring-like line cutting arrangement in some of the embodiments illustrated. However, it will be appreciated, applicants invention is not limited to applications wherein its flexibility allows an inherent bending into an annular or ring-like configuration but, rather, applicants invention may equally well be utilized in any configuration wherein a, for example, cutting operation is desired over an extended line.

Referring now to the embodiment of applicants invention shown in FIGURES 1 and 2, there is provided in this embodiment of applicants invention, a flexible explosive arrangement generally designated 10 according to the principals of applicants invention herein which, in this embodiment of applicants invention, may be utilized to operate as a line cutter on an article to be out such as a nose cone 12 of a missile 14. The nose cone 12 is to be cut along the peripheral cut line designated 16 and, consequently, the flexible explosive arrangement 10 is formed into an annular or ring-like configuration adjacent to the nose cone 12 and in substantially direct contact therewith.

The flexible explosive arrangement 10 is comprised of a first flexible elongated high explosive charge member 18 having a first preselected initiation surface area 19 on a top external surface 20 thereof. In this embodiment of applicants invention the first explosive charge member 18 has a substantially rectangular cross section having parallel opposite sides. That is, the first explosive charge member 18 has an interface preselected surface area 22 thereof that is substantially parallel to the top surface area 20 and spaced radially inwardly from the top surface area 20. There are also provided a pair of substantially parallel side walls 24 and 26.

There is also a second high explosive charge member 28 having contact surface areas 30 adjacent to and in detonation relationship with the interface preselected surface areas 22 of the first explosive charge means 18. The second explosive charge means 28 is also an elongated, flexible explosive charge means and, as described below, has different lower detonation front velocity.

Second or Mach stem emergent preselected surface areas 32 of the second explosive charge member 28 are in line cutting relationship with the nose cone 12 along the cut line 16 thereof. The second explosive charge member 28 is also provided with parallel side Walls 34 and 36.

When the time is appropriate to sever the nose cone 12 along the cut line 16, an appropriate signal is given to a detonator means 38 that is in detonation relationship to the initiation surface area 19 of the first explosive charge means 18. When the detonator means 38 is detonated, there is initiated spherical detonation front in the first explosive charge means 18 emanating from the initiation surface area 19 and moving therethrough both toward the interface preselected surface area 22 thereof, which is remote from the initiation surface area 19, in the direction indicated by the arrow 33, and also longitudinally along the elongated length of the first explosive charge member in the direction indicated by the arrow 35, at the first detonation front velocity. The detonation front is illustrated by the lines 40 as it moves from the initiation surface area 19 to the second preselected surface areas 22.

A wave shaper 42 which, in this embodiment of applicants invention, comprises an inert flexible rubber cylindrical rod-like member, is positioned extending along the boundary between the interface preselected surface area 22 of the first explosive charge member 18 and the contact surface area 30 of the second explosive charge member 28 and in alignment with the out line 16 in the nose cone 12. When the moving detonation front 40 moving in the direction of the arrow 33, in the first explosive charge member 18, encounters the inert wave shaper means 42 there are provided two distinct detonation or shock fronts from the original detonation front and these two detonation or shock fronts move through the second explosive charge member from the contact surface area 30 to the Mach stem emergent or second preselected external surface 32 that is in contact with the nose cone 12. The two detonation or shock fronts 44a and 4411 are re-entrant in the second explosive charge member 28 to converge and form a linear Mach stem 46 along the perpendicular bisecter of the second preselected external surface area 32, which perpendicular bisecter is in the Mach stem zone that is aligned with the cut line 16.

In this embodiment of applicants invention the Mach stem '46 that is generated is a variable angle Mach stern. A description of the design features for the generation of variable angle Mach stems utilized for projectile acceleration may be found in, for example, the book The Science of High Explosives, by Melvin A. Cook, 1958, Reinhold Publishing Corporation, New York, New York. Applicant has found that the variable angle Mach stern when the detonation or shock front intersection angle is kept comparatively small, such as is accomplished by utilization of the wave shaper 42, it provides a sufliciently high constantly increasing momentum in the Mach stem 46. Thus, the Mach stem 46 moves in the direction of the arrow 48 in the plane containing the cut line 16 from the convergence thereof at the inert Wave shaper means 42 to the Mach stem emergent or second preselected external surface area 32 with constantly increasing momentum. The density of the gases contained within the Mach stem 46 at all times remains substantially constant, but, of course, it is greater than the density behind the converging detonation fronts prior to the intersection thereof. However, the front 47 of the Mach stem 46 and the size of the Mach stem 46 is constantly increasing and therefore the momentum thereof is constantly increasing. This provides a comparatively high momentum Mach stem 46 at the Mach stern emergent or second preselected external surface area 32 centered along the cut line 16. The action of this high momentum Mach stem 46 on the nose cone 12 effects a linear cut therealong substantially throughout the elongated length of the flexible explosive arrangement continuously and cuts through the nose cone 12 to elfect a complete separation of the portion 12a from the missile 14.

The first flexible exposive charge member 18 has a greater detonation front velocity than the second flexible explosive charge member 28. That is, for example, the detonation front velocity of the detonation front 40 moving in the first explosive charge member 18 may be on the order of 8,500 meters per second and the detonation front velocity of the detonation front 444 and 44b in the second explosive charge member 28 may be on the order of, for example, 6,500 meters per second. It will be appreciated, of course, that the flexibility of the explosive arrangement 10 may be provided by having a suitable explosive mixture embedded in a flexible matrix. That is, applicant has found that the first explosive charge member 18 may be fabricated from HMX dispersed in a suitable exible plastic binder matrix mix. For example, the HMX may be between 90 and 80% by weight to provide a charge specific gravity on the order of 1.865 to 1.876. This will provide a suitable high detonation front velocity in the first explosive charge member 18 on the order of 8,500 meters per second. It will be appreciated that the first explosive charge member 18 may be fabricated from PBX or other similar explosive suitably dispersed in a flexible matrix binder mix to provide the desired flexibility and high detonation front velocity.

The second high explosive charge member 28 is also flexible and may be fabricated from a mixture comprising, for example, 90 to PETN in a suitable flexible plastic binder. Such a mixture provides a comparatively low detonation front velocity on the order of 6,500 to 5,000 meters per second. Similarly, such explosives as Comp. B or Comp. C may also be utilized when suitably mixed in a flexible binder matrix mix to provide the second high explosive charge member 18 with a detonation front velocity less than the detonation front velocity in the first high explosive charge member 18.

In the various embodiments of applicants invention described herein, the first explosive charge member that is detonated first always is fabricated from a material having a higher detonation or shock front velocity than the second explosive charge member having the Mach stem emergent or second preselected external surface area. Applicant has found that this is necessary in order to provide satisfactory cutting over an extended elongated length of the explosive arrangement of applicants invention herein.

When the detonation front is first initiated in the first explosive charge member, the detonation front is spherical and moves outwardly from the point of detonation. In a region spaced away from the point of initiation, the detonation front is essentially a plain front traveling along the length of the elongated first explosive charge member. Thus the spherical front becomes essentially a plane front traveling parallel to the long direction of the first explosive charge member and extending between the top external surface and the interface surface.

However, in order to maintain the formation of a Mach stem, it is necessary that the detonation or shock fronts in the second explosive charge member be moving from the contact surface area thereof to the Mach stern emergent or second preselected external surface in order to provide cutting action along the cut line in contact with the second or Mach stem emergent preselected external surface. Therefore, the greater detonation front velocity in the first explosive charge member provides a continuous detonation along the entire contact surface area of the second explosive charge member that is in contact with the interface surface area of the first explosive charge member. These detonations, due to the greater velocity in the first explosive charge member, precede the propagation of any detonation or shock-front longitudinally along the second explosive charge member and thus at any point along the length of the second explosive charge member the detonation or shock-fronts that are re-entrant therein to converge to form the Mach stem are always traveling essenially in the direction from the contact surface area thereof to the Mach stem emergent surface thereof. It is only by providing this difference in detonation or shock-front velocities in the first and second explosive charge members that allows utilization of a single point initiation and still generates an extended Mach stem continuously throughout the length of the explosive arrangement.

It will be appreciated, of course, that the energy associated with the Mach stem provides the necessary energy for cutting the article to be out along the predetermined cut-line. If the Mach stem were not generated, there would merely be an explosion in the explosive arrangement but it would not necessarily provide the satisfactory continuous and accurate cutting that is desired.

As noted above, the explosive arrangement may be flexible in order to be conveniently formed to be aligned with a predetermined cut-line in an article to be cut, or in many applications, it may be desirable to have a substantially rigid explosive arrangement provided by casting the explosives into the predetermined desired shape that conforms to the predetermined cut-line configuration for the particular application. That is, in the embodiment of applicants invention herein, the explosive arrangement may be fabricated in either a flexible or a rigid configuration as may be desired for a particular application.

Applicant has found many combinations of explosives has a curved top external surface 20 that includes the initiation surface area 19' underneath a detonator 38. The second explosive charge member 28 may be fabricated in the same shape and configuration as the second explosive charge member 28 and the inert member 42' and binder that are satisfactory for forming both the first may be fabricated similarly to the inert member 42 shown explosive charge member and second explosive charge above. Thus, as described above, in the other embodimember. Table I lists the characteristics and constituents ments of applicants invention as described herein, the of several combinations of explosives and binders that top external surface of the first explosive charge memare satisfactory for utilization as the first explosive charge ber may generally be fabricated in any desired shape and member. 10 is not limited to any one particular geometric shape.

Table II lists several explosives that are satisfactory As noted above, the Mach stem 46 generated in the for utilization in the second explosive charge member. explosive arrangement 10 shown in FIGURES 1 and 2 TABLEI Percent Percent Specific Detonation Explosive by wt. Binder by wt. gravity front velocity, meters/second 1 HMX. 94 3 1. 841 8,800 2 HMX..... 93.7 2.7 '"if87 "a' 95 13' "ii ,'05"" 78 22 1. 821 8,480 84 10 1.882 86 14 1.894 86 12 1.798 8, 380 83 17 1. 911 8,420 85 1.865 8,470

TABLE H is a variable angle Mach stem. Applicant has also found that a constant angle Mach stem may also be effectively Explosive specific gravity utilized in a flexible explosive arrangement to provide,

second for example, a line cutting function. L580 6,800 Applicants co-pending patent application, Ser. No. 1.600 7, 593,158 filed Nov. 9, 1966, describes in detail the tech- 1'600 7500 niques for generating a constant angle Mach stem. The

advantages in a constant angle Mach stem over a varia- Where: ble angle Mach stem are inherent in the constant angle Mach stem by providing a greater momentum associated NczNmioceuulose with the Mach stem than can be provided in a variable CEF:Tr1s-chloroethylphosphate angle Mach 8mm DNPA:2,2411ltroprgpylacrylate As shown on FIGURE 3, 3A and FIGURE 4 there EtDAzEthyl 44'dmltropentanoate is provided an explosive arran ement enerall d o a a y FNR=Tetrafluoroethylenetrifiuoronitroso methane co- Hated 50, comprised of a first elongated explosive Charge P F member 52 and a second elongated explosive charge iggf fluonde'hexafluoropropylene Copoly' member 54. The first explosive charge member 52 has an initiation surface area 55 on an external surface 56 8 :6 2 ;gggggfgfigiggggg gg ES i3; that is spaced from the article to be cut 58. The first t fl th 1 and second explosive charge members may be c1ther flexie On e m uoroe y ene p0 ymer ble or rigid, as desired.

The explosives shown in Table II may be utilized The article 0 he Cut 53 y for p be a Plate either alone or in combination with" for example, the and is 10 be cut along line 60 that iS the intersection of binders shown in Table I to provide the second exploa plane containing the perpendicular bisector 62 of the sive charge means according to applicants invention explosive arrangement 50 and the article to be cut 58. herein. That is, the explosives shown in Table II may An initiator 64 which, for example, may be similar to be mixed in ratios of approximately 90% explosive to the initiator 8 Shown in FIGURES 1 and 2 y in 50% explosive by weight with, respectively, 10% to 50% detonation inducing relationship to the initiation surface binder by weight to obtain the different specific gravitics area of the first explosive charge member 52. and detonation front velocities that may be desired. In this fimhodimeht 0f PP invfihtioh e fi One example of a commercially available second exexplosive charge member 52 has interface preselected plosive charge member that is satisfactory for utilization urface areas generally designated 66 spaced from the in applicants invention herein is the product manufac- P external Surface a 56 a d portions 66' and 66" tnred under h trade name D t h t, f t d are in contact with the upper surface 68 of the article to by the E. I. du Pont de Nemours Company, Wilmingbe cut 58. ton, Del., and is comprised of 65% PETN and 35% The interface preselected surface area 66 also combinder. Further, it will be appreciated, many other variaprises a pair of substantially parallel side wall surface tions and combinations of explosives and binders may portions and 72 defining an elongated S1011 n ng be fabricated by those skilled in the art according to the a preselected distance from the surface 68 of the article i i l f li i nti h i 65 to be cut 58 towards the top external surface area 56 In FIGURES 1 and 2 above, the explosive arrangeand having a base wall surface portion 74 defining a base meat 10 was shown as fabricated with a first explosive to said s ot. I will be appreciated that the slot so dearrangement 18 having a substantially rectangular crossfined by the side wall portions 70 and 72 and th ba e section I ill b appreciated th th cross-sectional wall portion 74 extends substantially continuously through shapes may equally well be utilized for the first explo- 70 out the elongated length of the explosive arrangement 50 sive arrangement 18. For example, as shown on FIG- in this embodiment of applicants invention.

URE lA, there is an explosive arrangement 10' that is Either the flexibility or the fabricated shape of the similar in shape and function to the explosive arrangeexplosive arrangement 50 allow flexible bending of the ment 10 shown above. However, in this embodiment of explosive arrangement 50 into the desired configuration applicants invention the first explosive charge means 18 75 such as that shown in FIGURE 3A. When formed into such a configuration it can be seen that the top external surface area 56 is outwardly spaced from the interface preselected surface areas 66.

The second explosive charge member 70 is positioned in the slot defined by the side wall surface portions 70, 72 and base wall surface portion 74 and the three external surfaces 76, 78 and 80 of the second explosive charge member 70 are in contact with and in detonation induced relationship with the substantially parallel side wall surface portions 70 and 72 and base wall surface portion 74 of the interface preselected surface area 66 of the first explosive charge member 52.

The Mach stem zone is along the perpendicular bisecter 62 of the explosive charge member 54 and a constant angle Mach stem is generated therealong.

When the detonator 64 is detonated to initiate the generation of a detonation front 82 traveling from said initiation surface 56 in said first explosive charge member 52 both towards the interface surface 66 and the contact surface areas 74, 76 and 78 of the second explosive charge member 54 the corners of the base surface 74 act as wave shapers to provide two converging detonation fronts in the second explosive charge member 54 for generation of the constant angle Mach stem 88 therein.

Since the detonation velocity is greater in the first explosive charge member 52 than in the second explosive charge member 54, the detonation front 82 moves at a greater velocity in the direction of the arrow 83 to provide the desired detonation characteristics in the second explosive charge member 54 for the generation of the Mach stem therein.

FIGURE 4 illustrates the generation of the constant angle Mach stem in the second high explosive charge member 54. As shown in FIGURE 4 the detonation front indicated by the line 82 is also moving through the first explosive charge member 52 in the direction indicated by the arrow 84. As the detonation front 82 commences to so travel through first explosive charge member 52 it is intercepted by the interface, between the base Wall surface 74 of the slot in the first high explosive charge member and the surface portion 80 of the contact surface area of the second high explosive charge member 54 At such an intersection there is then generated in the second high explosive charge member 54, a pair of converging re-entrant detonation or shock fronts 86a and 86b converging on the perpendicular bisector 62.

Thus, the detonation or shock fronts 82a and 86b moving in the second explosive charge member 54 in the direction indicated by the arrow 84 generate a Mach stem 88 that is wedge-shaped and extends throughout the elongated length of the explosive charge member 50. The angle generated by the intersection of the detonation fronts 86a and 86b is indicated to be the angle equivalent to twice the angle a on FIGURE 4. This is the apex angle of the Mach stem 88. The angle a is determined by the relative detonation or shock front velocities in the first high explosive charge member 52 and second high explosive charge member 54.

However, at the intersection, that is the apex of the wedge-shaped detonation front 86a and 86b the detonation front generates two streams as indicated by the arrows 90 and 92. The arrow 90 is generally moving backwardly, that is towards the base wall surface 74 of the slot in the first high explosive charge member 52, with respect to the direction of movement of the detonation fronts 86a and 86b, and the stream indicated by the arrow 92 moving in the same direction as the detonation front 86a and 86b. It will be appreciated that as the material in the Mach stem 88 moves in the direction indicated by the arrow 84 along the perpendicular bisecter 62, the density of the gases contained therein remain substantially constant, but greater than behind the detona tion fronts before intersection, but the size of the Mach stem 88 constantly increases even though the angle a remains constant. Therefore, when the Mach stem 88 reaches the second preselected external surface area 81 of the second explosive charge member 54, there is a comparatively high momentum value associated therewith. This high momentum value is utilized to effectuate a cutting of the article to be cut 58 along the cut line 60 thereon.

From the considerations heretofore set forth, it can be seen, as shown in FIGURE 4, that the constant angle Mach stem is properly defined as the intersection of the shock wave fronts in the second explosive charge member 54. That is, the Mach stem commences, in inertial space, at the point designated 94 corresponding to a point on the erpendicular bisecter 62 at the interface between the base surface portion 74 of the slot in the first explosive charge member 52 and the contact surface portion in the second explosive charge member 54. From a consideration of velocities involved, it will be noted that the detonation front 82 in the first explosive charge member 52 moves in the direction indicated by the arrow 84 at a first predetermined detonation front velocity.

The detonation wave fronts 86a and 86b which, in the embodiment shown in FIGURE 4, are linear, intersect and have their apex initially at the point 94, move in the direction indicated by the arrow 96 with a second predetermined velocity less than the first predetermined velocity. However, when the detonation fronts 86a and 86b in the second explosive charge member 54 have moved from the position indicated as defining the point 94, to the position defining the point 98, it can be seen that the detonation front has traversed a certain distance, indicated by the letter d, in the second explosive charge member 54. In this same time interval, it will be appreciated, the Mach stern has moved from a position having its apex at the point 94 t a position having its apex at the point 98. Thus, with respect to the inertial space point 94, the Mach stem has a velocity in the axial direction greater than the detonation front velocity in the second explosive charge member 54. It will be remembered, of course, that in this configuration the points 94 and 98 correspond to lines contained within the plane containing the perpendicular bisecter 62 and perpendicular to the upper surface 68 of the article to cut 58.

As noted above, materal from the second explosive charge member 54 flows into the Mach stem 88 in the directions indicated by the arrows and 92. That portion moving in the direction indicated by the arrow 92 is moving relative to the motion of the Mach stern in the same direction, as indicated by the arrow 84, and has, therefore, total greater velocity. Consequently a Mach stem front 100 is generated that extends, in this embodiment of applicants invention, between the detonation fronts 86a and 86b. The velocity of the Mach stem front 100 with respective velocity of the Mach stem is greater and, consequently, there is a material build-up between the detonation front 86a and 86b and the Mach stem front 100. The density of the gases in the Mach stem 88 remain substantially constant, but because of the greater velocity of the Mach stern front 100 in the direction indicated by the arrow 84, there is a constant increase in the momentum associated with the moving Mach stem 88.

Thus, the Mach stem zone in the second explosive charge member 54 is centered about the perpendicular bisecter 62 and reaches the upper surface 68 of the article to be cut 58 having a comparatively high momentum and mass associated with the particles contained within the Mach stem 88 and the energy associated therewith effectively cuts through the article to be cut 58 to provide the desired severance along the cut line 60.

The above description of the physical principals in volved in the generation of a constant angle Mach stem such as the constant angle Mach stem 88 is presented by applicant to aid in the greater understanding of applicants invention herein and the utility thereof. It will be 1 I appreciated that a similar analysis applies for a variable angle Mach stem 46 shown in FIGURES 1 and 2.

In the configuration of the explosive charge arrangement 50 shown in FIGURES 3 and 3A, which as noted above, may be either flexible or rigid to conform to the desired shape of the line to be cut 60, applicant has found that if it is desired to use single point initiation from a single initiation surface area 55 by the detonator 64, it may be necessary, when there is an extended length of the explosive arrangement 50, to provide an intermediate explosive charge member between the detonator and the first explosive charge member in order to insure that the detonation fronts in the second explosive charge member 54 re-enter and converge to form the Mach stern and therefore travel in the direction indicated by the arrow 4 rather than in longitudinal directions as indicated by the arrow 83.

FIGURES 3B and 3C illustrate a modification of the embodiment shown in FIGURES 3 and 3A in which an intermediate explosive charge member is utilized to provide such an explosive characteristic arrangement. As shown in FIGURES 3B and 3C, the explosive charge arrangement 200, which may be either flexible or rigid as desired, is comprised of a detonator 202, a first explosive charge member 204 and a second explosive charge member 206, all of which may be identical to the corresponding detonator 64, first explosive charge member 52 and second explosive charge member 54 shown in FIGURES 3, 3A and 4 described above. However, in this embodiment of applicants invention there is provided an intermediate explosive charge member 208 that is Positioned between the detonator 202 and the first explosive charge member 204. The intermediate charge member 208 extends substantially throughout the length of the explosive arrangement 200 and is in contact with the top external surface 210 of the first explosive charge member 204 throughout the elongated length thereof. The intermediate charge member 208 is fabricated from an explosive arrangement that has a greater detonation or shock front velocity than either the first explosive charge member 204 or second explosive charge member 206. Therefore, when the detonator 202 is initiated to commence the generation of the spherical shock waves 211 in the intermediate charge member 208, the shock waves 211 also progress in both the directions indicated by the arrow 212 towards the first explosive charge member 204 as well as longitudinally in the direction indicated by the arrow 214. Since the propagation velocity is greater in the intermediate explosive charge member 208 than in the first explosive charge member 204, the first explosive charge member 204 is substantially continuously detonated along the top external surface 210 thereof before any detonation or shock wave front in the first explosive charge member 204 can travel in a direction indicated by the arrow 214. Therefore, the shock waves generated in the first explosive shock member 204 generally travel in the direction indicated by the arrow 212 and intersect the second explosive charge member 206 to provide the formation of the Mach stem therein as described above.

Thus, in the embodiment of applicants invention shown in FIGURES 3B and 3C the intermediate charge member 208 may be selected to have a detonation front velocity on the order of 8,500 meters per second. The first explosive charge member may be selected to have a detonation front velocity of approximately 7,000 meters per second and the second explosive charge member 206 may be selected to have a detonation front velocity on the order of 5,500 meters per second.

Similarly, in other embodiments where only two explosive charge members are utilized, the first explosive charge member may be selected to have a detonation front velocity on the order of 8,500 meters per second and the second explosive charge member may be selected to have a detonation front velocity on the order of 6,500 meters per second.

It can be seen that the wave shaper means may comprise the inert member 42 shown in the embodiment of applicants invention illustrated in FIGURES 1 and 2 and ma also comprise the interface between the first explosive charge member 52 and second explosive charge member 54, depending upon the geometry thereof, as illustrated in FIGURES 3, 3A, 3B, 3C and 4. The wave shaper may take many other forms and, for example, may be provided by an inert slot in the second explosive charge member.

Such a configuration is illustrated in FIGURE 5. As shown on FIGURE 5 there is an explosive charge arrangement, generally designated 110, comprised of a first elongated explosive charge member 112 and a second elongated explosive charge member 114. The explosive arrangement may be, if desired, flexible to allow bending into any desired configuration similar to that shown on FIGURE 1 for the explosive arrangement 10 or on FIGURE 3A for the explosive arrangement 50, to effect line cutting of an article to be cut 116 along a out line 118 contained within the plane defined by the perpendicular bisector 120 of the second explosive charge member 114, or it may be rigidly fabricated into such a shape.

When positioned into the desired configuration, the first explosive charge member 112 has initiation surface 121 on top external surface 122 radially spaced outwardly from and parallel to an interface preselected surface area 124. A detonator means 126 which, for example, ma be similar to the detonator means 38 shown in FIGURES 1 and 2, is coupled to the initiation surface 121 to provide initiation of a detonation front emanating therefrom.

The second explosive charge member 114 has a contact surface area 128 that is substantially continuously adjacent to and in detonation inducing relationship with the interface preselected surface area 124 of the first explosive charge member 112 throughout the elongated length thereof. In this embodiment of applicants invention the second explosive charge member 114 has external surface areas 130 spaced from the contact surface area 128. The external surface areas 130 have a portion 132 and 134 in contact with the upper surface 136 of the article to be cut 116 and spaced from the cut lines 136.

The external surface areas 130 of the second explosive charge member 114 also have substantially parallel side wall portions 136 and 138 and base wall portion 140 defining a slot 142 extending substantially continuously throughout the elongated length of the second explosive charge member 114. The slot 142 need not be hermetically sealed to the article to be cut 116 to trap air of some predetermined temperature and pressure therein but will operate satisfactorily as a wave shaper and Mach stem zone regardless of the environment existing therein.

Thus, in this embodiment of applicants invention, the geometrical configuration of the external surface areas 130 of the second explosive charge member 114 comprise the wave shaper means for generating the pair of converging shock fronts in the slot 142 necessary to produce a Mach stem.

Both the first explosive charge member 112 and the second explosive charge member 114 have parallel side walls 144a and 1441) and 146a and 146b, respectively. Thus each of the first and second explosive charge members 112 and 114 are substantially rectangular in crosssection, similar to the rectangular cross-sections of the first and second explosive charge members 24 and 26 shown in FIGURE 1 and 52 and 54 shown in FIGURE 3.

When the detonator means 126 is detonated, there is generated a detonation front 150 moving both from the initiation surface 122 towards the second preselected surface area 124 of the first explosive charge member 112 and longitudinally in the direction of the arrow 15 1. At the interface surface 124 the detonation front 150 always induces a detonation front 152 in the second explosive charge member 114 traveling from the contact surface area 128 toward the external surface areas 130 thereof in the direction of the arrow 153 for the reasons specified above. However, when the detonation front intersects the base wall portion 140 defining the slot 142 there is generated a pair of converging shock fronts, generally designated 160 and 162, that are swept back on re-entry into the slot 142 and generate a Mach stern 164 in a Mach stem zone centered along the perpendicular bisecter 120 of the slot 142, which is also the perpendicular bisector of the second explosive charge member 114. The Mach stern 164 so generated is a variable angle Mach stern and intercepts the article to be cut 116 along the cut line 118 thereof and the high energy associated with the Mach stem 162 effectively severs the article to be cut 116.

It will be appreciated that, in the above-described embodiment of applicants invention, a substantially continuous line cutter was described wherein the Mach stem was generated substantially continuously throughout the elongated length of the flexible explosive arrangement. However, it will be appreciated, applicants invention may equally well be utilized in an embodiment wherein a Mach stern and consequently cutting action is provided only at preselected line segment intervals along the elongated length thereof.

One such embodiment is shown on FIGURE 6. As shown on FIGURE 6, there is a flexible explosive arrangement generally designated 1'80 comprised of a first high explosive flexible elongated charge member 182 which, for example, may be rectangular in cross-section and similar to the first explosive charge member 18 shown in FIGURE 1 and be provided with a detonation means 184 along the initiation surface area 185, at the top external surface 186 thereof. An inert rod-like member 188 is provided and functions as a wave shaper in a manner similar to the function of the wave shaper 42 shown in FIGURES 1 and 2.

However, in this embodiment of applicants invention, there are provided a plurality of discrete' second high explosive charge members 190 in spaced apart relationship to each other. Each of the second flexible elongated explosive charge member 190 may be similar to segments of the second explosive charge member 28 shown in FIG- URES 1 and 2. However, they do not extend continuously throughout the elongated length of the first flexible elongated explosive charge member 182, but are spaced apart and, if desired, may be spaced apart by inert wedges 191. Therefore, when the detonator 184 is actuated, the detonation wave progresses through the first explosive charge member 182 and the second explosive charge member 190 to generate the Mach stem therein as described above. However, the Mach stem is generated only in the discrete regions along the length of the explosive arrangement 180 occupied by the second explosive charge member 190 to effect line cutting in segments.

In each of the embodiments of applicants invention described above, it will be appreciated, the same materials in the same proportions as indicated acceptable for the first high explosive charge member 18 of the flexible explosive arrangement in FIGURES l, 2 and 3 may be utilized for each of the first flexible explosive charge members shown in the other embodiments. Similarly, the same materials and same proportions indicated acceptable for the second explosive charge member 28 of the flexible explosive arrangement .10 in the embodiment shown in FIGURES l, 2, and 3 may also be utilized for fabrication of the other second explosive charge members. However, as noted above, the detonation front 'velocity in the first explosive charge member must always be greater than the detonation front velocity in the second explosive charge member in order to generate the desired Mach stem whether it be a constant angle Mach stem or a variable angle Mach stem.

I claim:

1. An explosive arrangement comprising, in combination:

a first elongated explosive charge member having a first preselected initiation surface area for initiation thereof to generate a first detonation front emanating from said initiation surface area and traveling therethroug-h at a first detonation front velocity to and along an interface preselected surface area in regions remote from said initiation surface area;

a second elongated explosive charge member having first preselected contact surface areas in detonation induced relationship to said interface preselected surface areas of said first charge member, to be detonated therealong by said first detonation front, to generate a second detonation front in said second explosive charge member emanating from said contact surface area and traveling therethrough at a second detonation front velocity less than said first detonation front velocity to Mach stem emergent second preselected external surface areas thereof in regions remote from said contact surface area; and

wave shaper means in contact with at least a portion of said second explosive charge means for shaping said second detonation front to provide a Mach stem in a Mach stern zone of at least a portion of said Mach stern emergent preselected external surface areas of said second explosive charge member.

2. The arrangement defined in claim 1 wherein:

said contact surface area of said second explosive charge member is in substantially continuous contact and co-extensive with said interface preselected surface area of said first explosive charge means throughout the elongated length thereof.

3. The arrangement defined in claim 1 wherein:

said second elongated explosive charge member comprises a plurality of separate, spaced apart members.

4. The arrangement defined in claim 2 wherein:

said first and said second explosive charge members and said wave shaper are flexibly bendable into a preselected configuration on an article to be out along a preselected out line thereof, and for the flexible explosive charge arrangement in said preselected configuration, the combination in which;

said Mach stem emergent external surface area of said second explosive charge means is in cutting relationship to the article to be cut along the out line thereof, and said contact surface area of said second explosive charge member is spaced a preselected distance from said Mach stem preselected external surface area; and

said initiation surface of said first explosive charge member is spaced from said contact surface area of said second explosive charge member.

5. The arrangement defined in claim 3 wherein:

said first and said second explosive charge members and said Wave shaper are flexibly bendable into a preselected configuration on an article to be cut along a preselected out line thereof, and for the flexible explosive charge arrangement in said preselected configuration, the combination in which;

said Mach stem emergent external surface area of said second explosive charge means is in cutting relationship to the article to be cut along the cut line thereof, and said contact surface area of said second explosive charge member is spaced a preselected distance from said Mach stem preselected external surface area; and

said initiation surface of said first explosive charge member is spaced from said contact surface area of said second explosive charge member.

6. The arrangement defined in claim 1 wherein:

said first explosive charge member comprises a substantially rectangular member and said initiation surface area comprising a portion of a first external surface thereof, said interface preselected surface area thereof comprising a second surface substantially parallel to said first external surface, and a pair of substantially parallel side surfaces;

said second explosive charge member comprises a substantially rectangular member and said contact surface thereof is adjacent said interface surface of said first explosive charge member, said shock stem emergent external surface thereof is substantially parallel to said contact surface area and spaced therefrom, and a pair of substantially parallel side wall surfaces; and

said wave shaper means comprises a rod-like member extending along a portion of the interface between said contact surface area and said second preselected surface area of said first explosive charge member and said rod-like wave shaper means in contact with said first explosive charge member and said second explosive charge member.

7. The arrangement defined in claim 1 wherein: said first explosive charge member comprises a top external surface, a pair of substantially parallel external side wall surfaces, and said interface surface areas thereof comprise a pair of side wall surface portions and a base surface portion defining a slot extending along the length of said elongated first explosive charge member; and

said second explosive charge member comprises a sub- 8. The arrangement defined in claim 7 and further comprising:

a substantially rectangular intermediate explosive member having a top surface area and a bottom surface area, and said bottom surface area of said intermediate explosive member being in substantially continuous contact with said top external surface of said first explosive charge member, and said top surface area of said intermediate explosive charge member having an initiation surface portion thereof.

9. The arrangement defined in claim 1 wherein: said first explosive charge member comprises a substantially rectangular member and said initiation surface area comprising a portion of a first external surface thereof;

said interface preselected surface area thereof comprising a second surface in a plane substantially parallel to said first surface, and a pair of substantially parallel side surfaces therebetween;

said second explosive charge member comprises a substantially rectangular member and said contact surface thereof is adjacent to and in a detonation front induced relationship with said interface surface area of said first explosive charge member, and said Mach stem emergent surface thereof comprises a pair of side surface portions and a base surface portion defining a slot extending throughout substantially the entire length of said second explosive charge member; and

said wave shaper means comprises said base surface portion defining said slot member, whereby a detonation front traveling from said contact surface area toward said Mach stem emergent surface area encounters said base surface portion to provide a pair of re-entrant converging detonation fronts in said slot to define a Mach stem along the perpendicular bisector thereof.

10. The arrangement defined in claim 8 wherein:

said second elongated explosive charge member comprises a plurality of separate spaced apart members.

References Cited UNITED STATES PATENTS FOREIGN PATENTS 5/ 1964 Great Britain. 3/ 1961 Great Britain. 4/ 1953 France.

4/ 1965 Germany.

VERLIN R. PENDEGRASS, Primary Examiner.

US. Cl. X.R. 

